Trap Response of terrapictalis (Buckett) (: ) to a Sex Attractant in Wheat-Growing Areas of Eastern Washington and Neighboring Oregon Author(s): Peter J. Landolt, Diana Roberts, Mary Corp, and Silvia I. Rondon Source: Journal of the Kansas Entomological Society, 84(2):139-147. 2011. Published By: Kansas Entomological Society DOI: http://dx.doi.org/10.2317/JKES101029.1 URL: http://www.bioone.org/doi/full/10.2317/JKES101029.1

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BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY 84(2), 2011, pp. 139–147 Trap Response of Dargida terrapictalis (Buckett) (Lepidoptera: Noctuidae) to a Sex Attractant in Wheat-Growing Areas of Eastern Washington and Neighboring Oregon

1,2 3 4 5 PETER J. LANDOLT, DIANA ROBERTS, MARY CORP, AND SILVIA I. RONDON

ABSTRACT: Traps in eastern Washington and northeast Oregon wheat fields, baited with a sex attractant for the of the wheat head armyworm (Walker), captured the congener moth Dargida terrapictalis (Buckett). When the two components of a sex attractant for the wheat head armyworm were tested singly versus together in a trap, nearly all D. terrapictalis captured were in traps baited with the combination of (Z)-11-hexadecenyl acetate and (Z)-11-hexadecenal, indicating synergy of the two compounds as attractants. Traps baited with this sex attractant and maintained through the growing season captured D. terrapictalis primarily in May in Umatilla County, Oregon, and in June and early July in eastern Washington. Small numbers of D. diffusa were present also in these traps, largely coincident in time with D. terrapictalis captured. This is the first demonstration of a sex attractant for D. terrapictalis and confirms the presence of D. diffusa in the states of Oregon and Washington through the identification of trapped . KEY WORDS: Dargida, sex attractant, lure, trap, monitoring, wheat head armyworm

Dargida () terrapictalis (Buckett) is a noctuid moth that is native to temperate western North America (Buckett, 1969). It has no recognized pest status, but is similar in appearance to, and may be confused with, the wheat head armyworm moth, Dargida (Faronta) diffusa Walker (1856). Both species were reassigned from Faronta to Dargida by Rodriguez and Angulo (2005). Larval host plants for D. terrapictalis are not known. However, the larvae of D. terrapictalis probably feed on grasses, based on host plant records for congeneric species (Crumb, 1956; Robinson et al., 2002). Caterpillars that were thought to be the wheat head armyworm caused localized but severe damage to wheat in Lincoln County of eastern Washington and Umatillah County of northeastern Oregon in 2007 and 2008 (Rondon et al. 2009). About 10,000 acres of winter and spring grains were sprayed with insecticides to control this pest in 2008. Concern over this damage prompted investigationin2009 into the distribution and seasonal abundance of the wheat head armyworm, which was previously unknown in the states of Oregon and Washington. A sex attractant for D. diffusa (Underhill et al., 1977) was used to detect and monitor the adult moth in wheat fields in 2009. The numbers of D. diffusa that responded to that sex attractant were low and there were no reports or complaints of damage to wheat by

1 USDA, ARS, Yakima Agricultural Research Laboratory, 5230 Konnowac Pass Road, Wapato, Washington 98951 USA. 2 Corresponding author. [email protected] 3 Washington State University Extension Service, 222 N. Havana Street, Spokane, Washington 99202, USA 4 Oregon State University, Umatilla County Extension Office, 721 NE 3rd, Suite 3, Pendleton, Oregon 97801 USA 5 Oregon State University, Hermiston Research and Extension Center, 2121 South First Street, Hermiston, Oregon 97838 USA Accepted 11 May 2011; Revised 7 June 2011 E 2011 Kansas Entomological Society 140 JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY armyworms in that area either during the 2009 or 2010 field seasons. However, much larger numbers of D. terrapictalis moths were captured in these same traps. We describe herein the trapping of D. terrapictalis with the D. diffusa sex attractant composed of (Z)-11-hexadecenyl acetate (Z11-16Ac) and (Z)-11-hexade- cenal (Z11-16Ald) (Underhill et al., 1977). This paper provides the first report of a sex attractant for D. terrapictalis, including determination of the significance of both compounds to sex attraction, and a first determination of the seasonal pattern of flight of males, as indicated by their capture in traps. In addition, we provide verification of the presence of D. diffusa in the states of Oregon and Washington.

Materials and Methods Sex attractant lures for season-long monitoring were made by loading pre- extracted red rubber septa (West Co., Lionville, PA, USA) with one mg doses of a 9 to 1 mixture of Z11-16Ac and Z11-16Ald (Bedoukian Research Inc., Danbury, CT, USA). Solutions were made of 9 and 1 mg Z11-16Ac and Z11-16Ald per ml methylene chloride respectively, and each septum was serially treated with 100 mlof solution for each compound. Septa were aired in a fume hood overnight, and then stored in glass bottles in a freezer until use in the field. Feeding attractant lures were composed of the mixture of acetic acid and 3- methyl-1-butanol (AAMB). This chemical blend is attractive to a number of species of moths, including several pest species in the noctuid subfamily Noctuinae (Landolt, 2000; Landolt and Higbee, 2002), to which Dargida is presently assigned (Lafontaine and Schmidt 2010). Polypropylene vials (15 ml) (Nalge Nunc International, Rochester, NY, USA), each with a 3 mm diameter hole in the vial lid, were each loaded with 10 ml of a 50:50 (by volume) mixture of the two chemicals, appliedto cotton balls placed within the vial (Landolt and Alfaro, 2001). Sex attractant and feeding attractant lures were used to bait Universal Moth Traps, also called UniTraps (Great Lakes IPM, Vestaburg, MI). Sex attractant lures (septa) were placed in plastic baskets provided with the trap and positioned at the center of the underside of the trap lid. Feeding attractant lures (vials) were suspended within the buckets of the traps by a fine wire (26 gauge) folded over the top lip of the bucket. Unitraps were the multi-colored design, composed of a green lid positioned over a yellow cone that fit onto the top of a white bucket. A 4 cm2 piece of VaportapeH (Hercon Environmental Inc., Emigsville, PA, USA) was stapled to the side of the trap bucket interior to kill captured . Traps were hung from stakes that were placed ,3 m outside of fields of wheat. Trap height was adjusted throughout the season so that the bottom of the trap was 5–10 cm above the top of the crop. Traps were checked weekly, at which time all insects were removed. Vaportape and sex attractant lures were replaced at 4-week intervals, and feeding attractant lures were replaced every 2 weeks.

2009 Season Monitoring Traps were used to determine the presence of wheat head armyworm moths and to determine the seasonality of moth activity as indicated by their capture in traps. Thirty-one trapping sites were established throughout the wheat growing region of eastern Washington, including Adams, Columbia, Douglas, Franklin, Garfield, Grant, Lincoln, Spokane, Walla Walla, Whitman, and Yakima counties (Fig. 1). VOLUME 84, ISSUE 2 141

Fig. 1. Distribution of counties trapped (gray shading) and positive trap captures for D. diffusa (stippling) and D. terrapictalis (hash lines) moths in eastern Washington and Umatilla County Oregon, 2009.

There were 2 trap sites in each county studied, except Yakima County with 4 and Lincoln County with 10 trap sites. The trap sites in Lincoln County included farms that had received damage from infestations of armyworms in 2007 and 2008. An additional 3 trapping sites were established on farms with armyworm damageto wheat in 2008 in Umatilla County of northeastern Oregon. Each site was monitored with a trap baited with a sex attractant lure and a trap baited with the feeding attractant lure. The two traps were placed 10 m apart. Traps in Washington were maintained from 14 May to 26 September and in Oregon from 26 May to 1 September 2009.

2010 Season Monitoring Traps were again placed to determine the presence of wheat head armyworm moths, as well as D. terrapictalis, and seasonality of activity. Thirteen sites in Spokane and Lincoln Counties of Washington were monitored throughout the growing season for 2010, including the 12 sites in those counties monitored in 2009. Twenty-five sites in Umatilla County, Oregon, including the three sites trapped in 2009, were also monitored. Two traps were placed at each site; an unbaited trap as a control and a trap baited with the wheat head armyworm sex attractant lure. Feeding attractant-baited traps used in 2009 were unsuccessful in capturing Dargida sp. moths and were not then included in monitoring efforts in 2010. Washington traps were maintained from 3 May to 27 September, and Oregon traps were maintained from 7 April to 23 September. Traps, sex attractant lures, trap placement, and trap maintenance were as described above. 142 JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY

Sex Attractant Component Synergy Test An additional experiment tested the hypothesis that the capture of male D. terrapictalis moths in traps baited with the two-component wheat head armyworm sex attractant is in response to the combination of chemicals rather than to one of the chemicals. Trap treatments were 1) no lure, 2) a septum loaded with one mg of Z11- 16Ac, 3) a septum loaded with 100 mg of Z11-16Ald, and 4) a septum loaded with one mg of Z11-16Ac and 100 mg Z11-16Ald. Sets of these 4 treatments were placed at each of six sites on the edges of wheat fields in Lincoln County, Washington. Traps were 10 m apart and treatments were randomized within sets. This experiment was maintained from 1 to 21 June 2010. Traps were checked weekly, at which time all insects captured were removed for sorting, identification, and recording. Trap catch data for the 13 Washington sites used in 2010 were analyzed by a paired t-test following a square root transformation of the data, to compare season trap totals for baited and unbaited traps. The same analysis was conducted for the trap catch data for the 25 Oregon sites in 2010. Trap catch data for the 2010 test of sex attractant component synergy were subjected to the Mann-Whitney Test using Statmost (DataMost, 1995). Voucher specimens of D. diffusa and D. terrapictalis moths are deposited in the M. T. James Entomological Collection of Washington State University, Pullman, Washington, the Oregon State University Collection in Corvallis, Oregon, and the U.S. National Museum, Washington DC.

Results 2009 Season Monitoring Twenty-three D. diffusa males were captured in sex attractant traps in 2009, at 10 of the 31 Washington sites and in 3 of the 11 Washington counties included in this study (Fig. 1). None were captured in feeding attractant traps. Most D. diffusa males were captured in June and early July (Fig. 2) and several in late August. Too few D. diffusa were captured in sex attractant traps paired with unbaited traps to permit a statistical assessment of their response to the sex attractant. Male D. terrapictalis moths were captured in 26 of the 31 sex attractant-baited traps used in the 2009 monitoring study in Washington. These traps were in Adams, Columbia, Douglas, Franklin, Grant, Lincoln, Spokane, Walla Walla, Whitman, and Yakima Counties (Fig. 1). No D. terrapictalis moths were captured in the single trap in Garfield County. Dargida terrapictalis moths were first trapped in late May, with greatest numbers in mid to late June (Fig. 3). Numbers of moths trapped decreased greatly in late June into early July. D. terrapictalis moths were not captured in the feeding attractant traps in Washington. The three sex attractant-baited traps placed in Umatilla County, Oregon in 2009 captured 106.3 6 13.9 male D. terrapictalis per trap, and no D. diffusa (Fig. 1). The majority of these moths were captured during the first week of trap placement. Because the three traps were not placed in time to determine the beginning of moth activity, we do not report the seasonal pattern of those trap results.

2010 Season Monitoring Male D. diffusa were captured in 5 of 13 sex attractant traps placed in Spokane and Lincoln Counties of Washington in 2010. Most were captured in late June and VOLUME 84, ISSUE 2 143

Fig. 2. Mean (6SEM) numbers of D. diffusa in sex attractant traps per week, for 31 sites in eastern Washington in 2009 (solid bars) and for 13 sites in Lincoln and Spokane Counties of Washington in 2010 (slashed bars).

Fig. 3. Mean (6SEM) numbers of D. terrapictalis in sex attractant traps per week, for 31 sites in eastern Washington in 2009 (solid bars) and for 13 sites in Lincoln and Spokane Counties of Washington in 2010 (slashed bars). 144 JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY

Fig. 4. Mean (6SEM) numbers of D. terrapictalis in sex attractant traps per week, for 25 sites in Umatilla County, Oregon during 2010 (solid bars). early July, with 3 also captured in late August and early September (Fig. 2). Numbers of moths in sex attractant-baited traps were significantly greater than in unbaited traps by Student’s t-test (t 5 2.16, d.f. 5 12, P 5 0.05). Four D. diffusa were captured in the 25 sex attractant traps in Umatilla County, Oregon, all during the week of 20–26 May. Male D. terrapictalis were captured in all 13 sex attractant traps in Washington. First capture of moths was in the third week of May (0.8 6 0.4, n 5 13), and most trap catch occurred during June (Fig. 3). As in 2009, very few or no males were captured in traps after early July. Numbers of male D. terrapictalis per sex attractant trap for the year were 112.5 6 22.7 (Mean 6 SE, n 5 13), while none were captured in unbaited traps (t 5 4.96, d.f. 5 12, P , 0.001). Male D. terrapictalis were captured in 24 of the 25 sex attractant traps in Umatilla County, Oregon. First capture was the second week of April (0.16 6 0.08, n 5 25), most were captured in May, and there were none captured after 9 June (Fig. 4). For the year, totals per trap were 10.4 6 2.1, n 5 25), while none were captured in unbaited traps (t 5 9.24, d.f. 5 24, P , 0.001). In Washington, numbers of two additional Noctuidae and one Crambidae moth species were captured in traps baited with the sex attractant. subjuncta (Grote and Robinson), which has been an apple pest (Landolt, 1998), was captured in 7 of the 31 sex attractant traps in Washington that were maintained through the 2009 season (Mean 6 SE 5 5.0 6 2.6 moths per trap, n 5 31), but not in any of the 13 sex attractant traps in Washington maintained through the 2010 season. Apamea devastator (Brace), the glassy cutworm, which feeds on grasses (Robinson et al., 2002), was caught in 29 of these same 31 sex attractant traps in Washington in 2009 (Mean 6 SE 5 29.8 6 6.7, n 5 31), and in all 13 sex attractant traps in Washington in 2010 (63.8 6 10.1, n 5 13). Crambus cypridalis (Hulst), a type of snout moth related to the sod webworm, was captured in 14 of the 31 sex attractant traps in VOLUME 84, ISSUE 2 145

Table 1. Numbers of male D. terrapictalis captured in traps baited with the sex attractant comprised of Z11-16Ac and Z11-16Ald. Lincoln County, Washington, June 2010. N 5 6. Means in a row followed by the same letter are not significantly different by the Mann-Whitney Test at P 5 0.05.

Control Z11-16Ac Z11-16Ald Z11-16Ac + Z11-16Ald

D. terrapictalis 0.0 6 0.0a 0.0 6 0.0a 0.3 6 0.0a 42.8 6 10.8b

Washington in 2009 (6.4 6 1.7, n 5 31), and all 13 sex attractant traps in Washington in 2010 (4.8 6 1.5, n 5 13).

Sex Attractant Component Synergy Test Nearly all male D. terrapictalis captured in the test of synergy of sex attractant components were in traps baited with the two-component blend (Table 1). Numbers of males in traps baited with the two-component blend were statistically greater than in unbaited traps (z 5 0.004), or in traps baited with Z11-16Ac (z 5 0.004) or Z11- 16Ald (z 5 0.004). No D. diffusa were captured in traps during this test.

Discussion This is the first report of a sex attractant for D. terrapictalis, and the second species of Dargida responding to the combination of Z11-16Ac and Z11-16Ald, after Underhill et al. (1977) reported D. diffusa trapped with this blend. Efforts to trap D. diffusa, or for that matter, D. terrapictalis, might result in capture of one, the other, or both species where they co-occur. Care must then be taken to properly determine the identity of the moths captured. Dargida terrapictalis is darker in appearance, particularly with the nearly all dark brown or dusky hind wings, while D. diffusa has much less darker marking on the forewing, and with considerable or all pale yellow coloration on the hind wing. Dargida diffusa is figured by Covell (1984) and Powell and Opler (2009). The relatively weak response of D. diffusa to the sex attractant in this study was unexpected, given the presumed pest status of this species in some Oregon and Washington wheat fields, and the moth response to the Z11-16Ac/Z11-16Ald sex attractant reported by Underhill et al. (1977). Perhaps the D. diffusa populations were dramatically reduced in this study from previous years or are generally very low compared to D. terrapictalis, in the study area. There were no reports of armyworm damage to wheat in these areas during 2009 and 2010, indicating that populations of armyworm larvae in these wheat fields were probably greatly reduced over that of the previous two years. It is possible that damage to wheat previously attributed to the wheat head armyworm may have been due to infestations of D. terrapictalis. However, there are no reports of D. terrapictalis feeding on wheat. Additional study is needed to determine the identity of moth larvae damaging wheat in this area and to determine any contributions of these two species to losses of wheat. If it is determined that D. terrapictalis feeds on wheat, it may be monitored by the sex attractant used in this study, providing additional useful information on its distribution by habitat and crop, time of flight, and relative abundance. Our trapping results show that D. terrapictalis has a flight period in spring, which is April/May for Umatilla County, Oregon, and in May/June for eastern Washington, and seems to be primarily univoltine. Monitoring for the presence and abundance of 146 JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY adults in relation to the wheat crop should then be done during those months, and sampling for larvae on wheat might best be done following peak flight. A very small number of moths were trapped in August in Washington, suggesting some potential for a second generation which would not seem to constitute a threat to the wheat crop. The corresponding data for the seasonal patterns of captures of D. diffusa are weak. Nonetheless, it appears to be somewhat similar in its seasonality, with most males captured in sex attractant traps in an early flight (late June and early July) and a smaller number of males captured in a late flight (late August and early September). Apamea devastator and L. subjuncta were two additional and abundant pest moths captured in the wheat head armyworm sex attractant traps. (Z)-11-Hexadecenal with Z11-16Ac is a sex attractant for A. devastator (Steck et al., 1977). The same two compounds are part of an attractive sex pheromone for L. subjuncta (Landolt and Smithhisler, 1998). These two species of moths are considerably larger than either species of Dargida, and are primarily gray in color, making it unlikely that they would be confused with either Dargida sp. when captured in sex attractant traps. A third species of moth that was captured in the same sex attractant traps, C. cypridalis, is not considered a pest species although its larvae feed on grasses (Robinson et al., 2002). There are no sex pheromones or sex attractants reported for C. cypridalis. However, Booij and Voorman (1984) captured males of Crambus nemorella (Hu¨bner) in traps baited with the same compounds reported herein (Z11- 16Ac and Z11-16Ald), but presented separately and not as a 2-component blend. There was no response of D. terrapictalis or D. diffusa to the feeding attractant lure (AAMB) placed at the field sites in 2009. Given the consistent and sometimes high numbers of D. terrapictalis in sex attractant traps, this lack of response seems conclusive. Prior studies of moths trapped with AAMB lures did not show capture of either of these two species of Dargida (Faronta) (Landolt and Hammond, 2001; Landolt et al., 2007; Landolt et al., 2011). However, large numbers of Dargida (Dargida) procincta (Grote) were captured in AAMB traps by Landolt and Hammond (2001) and by Landolt et al. (2011).

Acknowledgements We thank David Bragg, Robin Garcia, Daryl Green, Christ Luttrell, Kathleen Mayhan, and Bonnie Oehler for technical assistance, and Eric Bruntjen and James Hansen for constructing the distribution map. This study was supported in part by funding from the Oregon and Washington Wheat Commissions. The identities of D. diffusa and D. terrapictalis were confirmed by Michael Pogue of the U.S. National Museum, Washington D.C.

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